- In essential fatty acid (EFA) deficient epidermal skin disease, lack of the dietary essential fatty acids 18:2 and 20:4 (n-6) results in a hyperproliferative epidermis. Topical application of 18:2 (n-6) normalizes epidermal proliferation through an unknown mechanism. The hypothesis driving this proposal is that the fatty acid content of membrane phospholipids controls the viscosity (fluidity) of the cell membrane and that this parameter, in turn, affects membrane mechanisms that control cell function. The long-term objective of the proposed studies is to determine the mechanism of membrane phospholipid fatty acid regulation of keratinocyte function. In vitro EFA-deficient keratinocytes will be grown in EFA-supplemented medium to yield cells with "normalized" membranes. For the EFA- deficient cells, the "normalization" of their phospholipid fatty acid content and successful measurements of membrane viscosity have been reported by these investigators. Thus it is proposed to use this characterized keratinocyte culture in Electron Paramagnetic Resonance experiments, with concomitant High Performance Liquid Chromatography and Gas Chromatographic analysis and extensive data reductions to: A. Test the hypothesis that changes in membrane fluidity caused by altered phospholipid fatty acid content alter the kinetic rates of fatty acid metabolism. Cell membrane fluidity will be altered using the epidermal EFAs 18:2(n-6) and 20:4(n-6), and 22:6(n-3) which is not present in epidermis and is apparently metabolically inert; B. define the key determiners, in disease and therapy, of membrane viscosity (EPR) and fatty acid profile by adding to the growth medium various lipids and nutrients; C. analyze second messenger and signalling systems in EFA-deficient and fatty acid-normalized cells. Performance of the proposed studies, it is hoped, will identify mechanisms by which the membrane fluidity of the cells alters the activity of membrane-associated enzyme and signal transduction systems. It is ventured that understanding these basic mechanisms will expand our knowledge of epidermal function and diseases.